1. Field of the Invention
This invention relates to i-line photoresist compositions for printed circuit applications which are imageable by exposure at i-line wavelengths of about 320 to 420 nanometers. In particular this invention is directed to a photoresist composition that will unexpectedly reduce line growth of the resist image of the printed circuit and unexpectedly has a longer shelf (storage) life than would have been expected.
2. Description of the Art
Photoresists are photosensitive films used to transfer images to a substrate. They are applied as liquid coatings or dry film compositions to a substrate to provide a photosensitive resist article. After forming the film on the substrate, the film is exposed through a patterned photomask to a source of activating energy such as light to form a latent image thereon after development. The photomask has areas opaque to activating radiation and other areas transparent to activating radiation. The pattern in the photomask of opaque and transparent areas defines a desired image that may be used to transfer the image to a substrate. A relief image is provided by development of the latent image pattern in the resist coating. The use of photoresist coatings is generally described, for example, by DeForest, Photoresist Materials and Processes, McGraw Hill book Company, New York (1975), and by Moreau, Semiconductor Lithography, Principals, Practices and Materials, Plenum Press, New York (1988) as well as in U.S. Pat. No. 5,366,846, the entire contents of this patent are incorporated herein by reference hereto. While the teachings of the above mentioned U.S. Pat. No. 5,366,846 are quite significant, it has been found that after development of the imaged photoresists, line growth of the resist had occurred. Therefore, there is still a need for better sidewall definition without substantial line growth during processing. The composition of the present invention provides a composition that even further reduces line growth of the resist sidewalls during development. Line growth produces etched lines which do not properly reproduce the desired geometries as defined by the mask.
Reference should also be had to the following for a greater understanding of the art: U.S. Pat. Nos. 5,034,304; 5,128,232; 4,189,323, 3,954,475, 5,057,397, 5,340,697, 4,826,753, 5,180,653, 5,340,697, and the following patents or publications: Canadian Patent No. 2100,392, Japan 63075737A2, Japan 05,303,196; 05,281,727 and European Patent Application Nos. 0 458 325, 0 519 298, 0 621,509, 0 483,689, 0 483,693 and 0,672,954.